U.S. patent application number 14/063403 was filed with the patent office on 2014-02-20 for method for shortening operation shutdown time of high pressure acid leach equipment in a hydrometallurgical process.
This patent application is currently assigned to SUMITOMO METAL MINING CO., LTD.. The applicant listed for this patent is SUMITOMO METAL MINING CO., LTD.. Invention is credited to Osamu Nakai, Yoshitomo Ozaki, Keisuke Shibayama.
Application Number | 20140048987 14/063403 |
Document ID | / |
Family ID | 41608574 |
Filed Date | 2014-02-20 |
United States Patent
Application |
20140048987 |
Kind Code |
A1 |
Shibayama; Keisuke ; et
al. |
February 20, 2014 |
METHOD FOR SHORTENING OPERATION SHUTDOWN TIME OF HIGH PRESSURE ACID
LEACH EQUIPMENT IN A HYDROMETALLURGICAL PROCESS
Abstract
This invention provides a method for shortening operation
shutdown time of high pressure acid leach equipment in a
hydrometallurgical process, wherein the high pressure acid leach
equipment comprises (i) means to transfer an ore slurry into the
high pressure acid leach equipment; (ii) means to increase
temperature and pressure of an ore slurry before leaching; (iii)
means to add sulfuric acid into the high pressure acid leach
equipment and to leach the ore slurry to obtain a leached slurry at
high temperature under high pressure; (iv) means to adjust the
pressure of the leached slurry; and (v) means to discharge the
leached from the high pressure acid leach equipment; wherein, upon
operation shutdown of the high pressure acid leach equipment, the
leached slurry is subjected to self-circulation inside the high
pressure acid leach equipment.
Inventors: |
Shibayama; Keisuke; (Tokyo,
JP) ; Nakai; Osamu; (Tokyo, JP) ; Ozaki;
Yoshitomo; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO METAL MINING CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
SUMITOMO METAL MINING CO.,
LTD.
Tokyo
JP
|
Family ID: |
41608574 |
Appl. No.: |
14/063403 |
Filed: |
October 25, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12458718 |
Jul 21, 2009 |
|
|
|
14063403 |
|
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Current U.S.
Class: |
266/44 |
Current CPC
Class: |
C22B 23/043 20130101;
Y02P 10/236 20151101; C22B 23/0453 20130101; C22B 23/0461 20130101;
Y02P 10/20 20151101; C01G 53/11 20130101; C22B 23/0407 20130101;
C22B 15/0093 20130101 |
Class at
Publication: |
266/44 |
International
Class: |
C22B 3/00 20060101
C22B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2008 |
JP |
2008-197208 |
Claims
1. A method for shortening operation shutdown time of high pressure
acid leach equipment in a hydrometallurgical process, wherein the
high pressure acid leach equipment comprises (i) means to transfer
an ore slurry into the high pressure acid leach equipment (ii)
means to increase temperature and pressure of an ore slurry before
leaching; (iii) means to add sulfuric acid into the high pressure
acid leach equipment and to leach the ore slurry to obtain a
leached slurry at high temperature under high pressure; (iv) means
to adjust the pressure of the leached slurry; and (v) means to
discharge the leached from the high pressure acid leach equipment;
wherein, upon operation shutdown of the high pressure acid leach
equipment, the leached slurry is subjected to self-circulation
inside the high pressure acid leach equipment.
2. The method according to claim 1, wherein the self-circulation of
the leach slurry is achieved by: shutdown of the transfer of the
ore slurry in the means (i), the addition of sulfuric acid in the
means (iii), and the discharge of the leached slurry in the means
(v); and transferring the leached slurry to the means to increase
temperature and pressure of an ore slurry before leaching (ii).
3. The method according to claim 1, wherein the means (ii) to (iv)
are the following apparatus respectively: means (ii): a multistage
heater for increasing temperature and pressure of the ore slurry,
means (iii): an autoclave for leaching the ore slurry at high
temperature under high pressure, and forming the leached slurry
with high temperature and high pressure, and means (iv): a
multistage flash tank for decreasing temperature and pressure of
the leached slurry stepwise.
4. The method according to claim 1, wherein the pH of the leached
slurry inside the high pressure acid leach equipment is adjusted at
3.0 to 5.0.
5. The method according to claim 1, wherein the temperature of the
means (iii) is 200 to 260.degree. C.
6. The method according to claim 1, wherein the operation shutdown
time is within 12 hours.
7. The method according to claim 2, wherein the pH of the leached
slurry inside the high pressure acid leach equipment is adjusted at
3.0 to 5.0.
8. The method according to claim 3, wherein the pH of the leached
slurry inside the high pressure acid leach equipment is adjusted at
3.0 to 5.0.
9. The method according to claim 3, wherein the temperature of the
autoclave is 200 to 260.degree. C.
10. The method according to claim 2, wherein the operation shutdown
time is within 12 hours.
11. The method according to claim 3, wherein the operation shutdown
time is within 12 hours.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a hydrometallurgical
Process for a nickel oxide ore, in more detail, in a
hydrometallurgical Process for a nickel oxide ore using a High
Pressure Acid Leach including a preparation step of ore slurry for
making a slurry of a nickel oxide ore, a leaching step for
obtaining leached slurry by transferring the relevant ore slurry to
a High Pressure Acid Leach equipment for leaching nickel and
cobalt, and a solid-liquid separation step of the relevant leached
slurry, the present invention relates to a hydrometallurgical
Process for a nickel oxide ore, which is capable of preventing
inevitable operation shutdown of the above leaching step and
maintaining high operation efficiency as a whole process basis, in
a trouble of the steps other than the above leaching step.
[0003] 2. Description of the Prior Art
[0004] A High Pressure Acid Leach using sulfuric acid has been
noticed in recent years, as a wet-smelting process recovering
Nickel and Cobalt from a nickel oxide ore, which contains an iron
as a main component and 1 to 2% by weight of Nickel. This method is
composed of consistent wet process steps without pyrometallurgical
treatment steps such as drying and roasting steps, unlike the
conventional general smelting method of nickel oxide ore, thus
providing advantage in view of energy and cost saving. That is, the
above High Pressure Acid Leach is capable of leaching nickel and
cobalt selectively relative to iron, by controlling the redox
potential and temperature of a leach solution inside a pressurized
leaching reactor in the leaching step, and by fixing the iron,
which is a main impurity, onto a leaching residue as a form of
hematite (Fe.sub.2O.sub.3), therefore it has very big merit.
[0005] The above High Pressure Acid Leach is composed of a step for
preparing an ore slurry, for example, by making slurry of a nickel
oxide ore (ore slurry preparation step); a step for obtaining
leached slurry, by adding the sulfuric acid to the above ore
slurry, leaching at a high temperature of 220 to 280.degree. C.
under high pressure, using an autoclave (leaching step); a step for
solid-liquid separation of a leaching residue and a leach solution
containing nickel and cobalt (solid-liquid separation step); a step
for neutralization separation of impurity elements such as iron, by
adjusting the pH of the leach solution containing the impurity
elements along with nickel and cobalt at 3 to 4 (a neutralization
step); and a step for recovering of a mixed sulfide of
nickel/cobalt, by supplying the hydrogen sulfide gas into the leach
solution after neutralization separation (a sulfurization step)
(for example, refer to Patent Literature 1).
[0006] Here, in the above ore slurry preparation step, the ore
slurry, which is adjusted to predetermined particle size, is
obtained by crushing and sieving of a nickel oxide ore with a wet
process. In addition, in the above leaching step, firstly the ore
slurry is subjected to passing through inside a multistage heater
to increase temperature and pressure stepwise. Subsequently, in the
autoclave, sulfuric acid is added to leach a part of the
impurities, along with nickel and cobalt, into a solution under
high pressure at high temperature formed with high-pressure steam.
Lastly, the leach solution is subjected to passing through the
multistage flash tank to decrease temperature and pressure
stepwise.
[0007] It should be noted that, in the above leaching step,
operation is performed at a high temperature of usually 240 to
260.degree. C., under high pressure, by using a pressure vessel
(autoclave) or the like, made of a very expensive material such as,
for example, titanium, ceramic and stainless steel, therefore in
the High Pressure Acid Leach equipment to be used in the operation,
sufficient management based on standards is indispensable, for
securing safety and maintenance of the equipment, in shutdown for
scheduled inspection, repair or the like, or also start-up. For
example, it is necessary to manage temperature increasing rate in
start-up and temperature decreasing rate in shutdown at a nearly
constant rate of equal to or lower than about 10 to 15.degree.
C./h, and not to exceed 25.degree. C./h, even at the maximal
rate.
[0008] For example, in start-up of the above High Pressure Acid
Leach equipment, firstly, temperature of a heater, an autoclave and
a flash tank, which compose the equipment, is increased in a state
that each of them is separated individually. Still more, the inside
of the autoclave is charged with water in advance, and temperature
thereof is increased under an operation state of an attached
apparatus such as a stirrer, seal thereof.
[0009] Next, at the timing when temperature of each apparatus is
increased up to about 150 to 180.degree. C., the heater, the
autoclave and the flash tank are connected as apparatuses. It
should be noted that, at this stage, because temperature is still
low and suitable operation condition has not been attained, the ore
slurry as a raw material cannot be supplied. Accordingly,
industrial water is supplied to the heater instead of the ore
slurry to be supplied in normal operation. Industrial water
supplied here is sent from the flash tank to the subsequent
preliminarily neutralizing step and the solid-liquid separation
step, via the autoclave, and finally becomes discharged water.
[0010] After that, at the timing when temperature of each apparatus
reached about 220.degree. C., supply to the heater is switched from
industrial water to the ore slurry. Still more, at the timing when
the temperature reached about 230.degree. C., sulfuric acid is
added to the inside of the autoclave, to start leaching of nickel
or cobalt from the ore slurry, and at this timing, start-up is
completed, and hereafter normal operation is started.
[0011] It should be noted here that advantage of increasing
temperature in a state that each of the heater, the autoclave and
the flash tank is separated, is reduction of use amount of
industrial water and amount of discharged water from the process.
That is, in the case where they are connected at a temperature of
below 150.degree. C., for example, use amount of industrial water
to be supplied instead of the ore slurry increases, resulting in
generation of a large amount of discharged water. In this sense, it
is desirable that they are connected at a temperature side as
higher as possible near 180.degree. C. However, in the case where
they are connected at a temperature of over 180.degree. C., for
example, at equal to or higher than 200.degree. C., difference
between vapor pressure in the autoclave and vapor pressure in the
flash tank becomes large, and thus pressure-like impact generates
onto the flash tank in connection, and in the worst case, a valve
or inner-lining brick of the flash tank are damaged.
[0012] On the other hand, on temperature decreasing in shutdown of
the above High Pressure Acid Leach equipment, any of the methods
may be selected from a method for cooling by supplying industrial
water instead of the ore slurry, while these apparatuses are
connected; or a method for cooling individually, by separation of
each of the apparatuses.
[0013] In the former case, due to use of industrial water,
discharged water generates in that amount, however, cooling rate is
fast and thus temperature can be decreased in a shorter time. Here,
temperature decreasing rate is generally 10 to 15.degree. C./h. In
addition, in the latter case, although there is no discharged water
generation, cooling rate is slow and thus a longer time is required
in temperature decrease. Here, temperature decreasing rate is
generally 5 to 10.degree. C./h. It should be noted here that ratio
of both temperature decreasing rates is generally 3 times.
[0014] It should be noted here that the situation leading to
inevitable shutdown of the above High Pressure Acid Leach equipment
includes, other than shutdown accompanied with the above scheduled
inspection and repair, the generation of emergency such as a
process trouble, which could give tremendously bad influence on
safety or environment; or the case of generation of a relatively
small scale trouble such as off specifications of intermediate
products in the ore slurry preparation step of a prior step of the
leaching step, or the neutralization step or the sulfurization step
and the like of the subsequent steps. In the case where such a
trouble is generated, it was general that, in all of the cases
other than the above emergency situation, the system is shutdown
safely by gradually decreasing temperature and pressure, by taking
importance on maintenance of the equipment, similarly as in
shutdown accompanied with the above scheduled inspection, repair or
the like.
[0015] However, in a trouble of the steps other than the above
leaching step using the High Pressure Acid Leach equipment, the
above relatively small scale troubles generate in many cases, and
in such troubles, because of no failure in the High Pressure Acid
Leach equipment itself, there was required that, by maintaining
operation of the High Pressure Acid Leach equipment as longer as
possible, operation shutdown time shall be shortened, and decrease
in operation efficiency shall be suppressed, as well as frequency
of shutdown and start-up of the equipment shall be decreased. As a
countermeasure for this, there has been performed a method for
maintaining operation, by using buffer tanks installed before and
after the High Pressure Acid Leach equipment, to temporarily store
a solution inside the buffer tanks, on the contrary, a method for
maintaining operation by using the solution inside the buffer
tanks, or a method for preventing shutdown of the High Pressure
Acid Leach equipment, by adjustment of flow rate of slurry to be
supplied into the autoclave. However, even by such countermeasures,
shutdown of the leaching step was necessary, in the case of over
limitation.
[0016] Under the above circumstance, it has been required, a
trouble of the steps other than the above leaching step using the
High Pressure Acid Leach equipment, to prevent operation shutdown
of the leaching step, which is configured by the High Pressure Acid
Leach equipment, and to maintain high operation efficiency as a
whole process basis. [0017] [Patent Literature 1] JP-A-2005-350766
(page 1 and page 2)
SUMMARY OF THE INVENTION
[0018] In view of the above conventional technological problems, it
is an object of the present invention to provide a
hydrometallurgical Process for a nickel oxide ore, which is capable
of preventing inevitable operation shutdown of the above leaching
step, and maintaining high operation efficiency as a whole process
basis, in a hydrometallurgical Process for a nickel oxide ore,
using the High Pressure Acid Leach including: a preparation step of
ore slurry for making the slurry of a nickel oxide ore; a leaching
step for obtaining leached slurry by transferring of the ore slurry
to a High Pressure Acid Leach equipment, for leaching nickel and
cobalt; and a solid-liquid separation step of the leached slurry,
and in a trouble of the steps other than the above leaching
step.
[0019] The present inventors have found that inevitable operation
shutdown of the above leaching step can be prevented, and high
operation efficiency can be maintained as a whole process basis, by
self-circulation of the above reached slurry, inside the High
Pressure Acid Leach equipment, under specific conditions, in a
hydrometallurgical Process for a nickel oxide ore, using the High
Pressure Acid Leach including: a step for preparing an ore slurry
by making a slurry of a nickel oxide ore; a leaching step for
obtaining leached slurry by transferring of the ore slurry to a
High Pressure Acid Leach equipment, equipped with the following
means (a) to (c), for leaching nickel and cobalt; and a
solid-liquid separation step of the leached slurry, and in a
trouble of the steps other than the above leaching step, and have
thus completed the present invention:
means (a) to preliminarily increase temperature and pressure of the
ore slurry; means (b) to form the leached slurry, by the addition
of sulfuric acid to the ore slurry with preliminarily increased
temperature and pressure, and leaching under blow of high-pressure
steam and, if necessary, high-pressure air; means (c) to adjust a
pressurized state of the leached slurry formed.
[0020] That is, according to a first aspect of the present
invention, there is provided a hydrometallurgical Process for a
nickel oxide ore, using a High Pressure Acid Leach including: a
preparation step of ore slurry for making a slurry of a nickel
oxide ore; a leaching step for obtaining leached slurry by
transferring of the ore slurry to a High Pressure Acid Leach
equipment equipped with the following means (a) to (c), for
leaching nickel and cobalt; and a solid-liquid separation step of
the leached slurry; characterized in that, in a trouble of the
steps other than the above leaching step,
the leached slurry, discharged from the means (c), which is used in
the above High Pressure Acid Leach equipment, is subjected to
self-circulation inside the High Pressure Acid Leach equipment, by
shutdown of transfer to the above solid-liquid separation step, and
transferred to the means (a), which is used in the above High
Pressure Acid Leach equipment, as well as by shutdown of receiving
the above ore slurry and the addition of sulfuric acid, in the
above leaching step: means (a) to preliminarily increase
temperature and pressure of the ore slurry; means (b) to form the
leached slurry, by the addition of sulfuric acid to the ore slurry
with preliminarily increased temperature and pressure, and leaching
under blow of high-pressure steam and high-pressure air; means (c)
to adjust a pressurized state of the leached slurry formed.
[0021] In addition, according to a second aspect of the present
invention, there is provided the hydrometallurgical Process for a
nickel oxide ore in the first aspect of the invention,
characterized in that, in self-circulation of the above leached
slurry inside the High Pressure Acid Leach equipment, pH of the
leached slurry is adjusted at 3.0 to 5.0.
[0022] In addition, according to a third aspect of the present
invention, there is provided the hydrometallurgical Process for a
nickel oxide ore in the first or the second aspect of the
invention, characterized in that, in self-circulation of the above
leached slurry inside the High Pressure Acid Leach equipment,
temperature of the means (b), which is used in the High Pressure
Acid Leach equipment, is 200 to 260.degree. C.
[0023] In addition, according to a fourth aspect of the present
invention, there is provided the hydrometallurgical Process for a
nickel oxide ore in any one of the first to the third aspects of
the invention, characterized in that, each of the above means (a)
to (c) uses the following apparatus:
means of (a): a multistage heater for increasing temperature and
pressure of the ore slurry stepwise, means of (b): an autoclave for
leaching the ore slurry at high temperature under high pressure,
and forming the leached slurry with high temperature and high
pressure, and means of (c): a multistage flash tank for decreasing
temperature and pressure of the leached slurry stepwise.
[0024] In addition, according to a fifth aspect of the present
invention, there is provided the hydrometallurgical Process for a
nickel oxide ore in any one of the first to the fourth aspects of
the invention, characterized in that, in the trouble of the steps
other than the above leaching step, estimated shutdown time of the
leaching step accompanying therewith is within a time required in
the case of shutdown of the High Pressure Acid Leach equipment,
separation of each apparatus and decreasing of temperature, and
subsequent increasing of temperature again.
[0025] In addition, according to a sixth aspect of the present
invention, there is provided the hydrometallurgical Process for a
nickel oxide ore in the fifth aspect of the invention,
characterized in that the above estimated shutdown time is within
12 hours.
[0026] The hydrometallurgical Process for a nickel oxide ore of the
present invention, in a hydrometallurgical Process for a nickel
oxide ore using the above High Pressure Acid Leach, and in a
trouble of the steps other than the above leaching step, is capable
of preventing inevitable operation shutdown of the above leaching
step, by self-circulation of the leached slurry inside the High
Pressure Acid Leach equipment by shutdown of receiving of the above
ore slurry and the addition of sulfuric acid, in the above leaching
step, as well as by shutdown of transfer of the leached slurry
discharged from the means of (c), which is used in the above High
Pressure Acid Leach equipment, to the above solid-liquid separation
step, and transferring to the means of (a), which is used in the
above High Pressure Acid Leach equipment, and is capable of
maintaining operation, by restart operation soon, if necessary, as
well as by no generation of discharged water due to no use of
industrial water, and still more by preventing corrosion troubles
of apparatuses such as a heater or pump of the High Pressure Acid
Leach equipment, under suitable control of pH of the leached slurry
to be circulated, and thus industrial value thereof is extremely
high.
BRIEF DESCRIPTION OF THE DRAWING
[0027] FIG. 1 is a process chart representing an example of one
embodiment of a hydrometallurgical Process for a nickel oxide ore,
in a normal state, according to a High Pressure Acid Leach.
NOTATION
[0028] 1 ore slurry preparation step [0029] 2 leaching step [0030]
3 solid-liquid separation step [0031] 4 neutralization step [0032]
5 sulfurization step [0033] 6 nickel oxide ore [0034] 7 ore slurry
[0035] 8 leached slurry [0036] 9 leach solution [0037] 10 leaching
residue [0038] 11 neutralized precipitate slurry [0039] 12 pregnant
solution for nickel recovery [0040] 13 sulfide [0041] 14 barren
solution
DETAILED DESCRIPTION OF THE INVENTION
[0042] Explanation will be given below in detail on the
hydrometallurgical Process for a nickel oxide ore, of the present
invention.
[0043] The hydrometallurgical Process for a nickel oxide ore of the
present invention is a hydrometallurgical Process for a nickel
oxide ore using a High Pressure Acid Leach including: a preparation
step of ore slurry for making a slurry of a nickel oxide ore; a
leaching step for obtaining leached slurry by transferring of the
ore slurry to a High Pressure Acid Leach equipment equipped with
the following means (a) to (c), for leaching nickel and cobalt; and
a solid-liquid separation step of the leached slurry; and is
characterized in that, in a trouble of the steps other than the
above leaching step,
the leached slurry, discharged from the means (c), which is used in
the above High Pressure Acid Leach equipment, is subjected to
self-circulation inside the High Pressure Acid Leach equipment, by
shutdown of transfer to the above solid-liquid separation step, and
transferring to the means (a), which is used in the above High
Pressure Acid Leach equipment, as well as by shutdown of receiving
the above ore slurry and the addition of sulfuric acid, in the
above leaching step: means (a) to preliminarily increase
temperature and pressure of the ore slurry; means (b) to form the
leached slurry, by the addition of sulfuric acid to the ore slurry
with preliminarily increased temperature and pressure, and leaching
under blow of high-pressure steam and high-pressure air; means (c)
to adjust a pressurized state of the leached slurry formed.
[0044] In the hydrometallurgical Process for a nickel oxide ore of
the present invention, it is important that, in a trouble of the
steps other than the above leaching step, the above leached slurry
is subjected to self-circulation inside the High Pressure Acid
Leach equipment. In order to attain this, in the above leaching
step, the leached slurry, discharged from the means (c), which is
used in the above High Pressure Acid Leach equipment, is
transferring to the means (a), which is used in the above High
Pressure Acid Leach equipment, by shutdown of transfer to the above
solid-liquid separation step, as well as by shutdown of receiving
the above ore slurry and the addition of sulfuric acid. That is, by
self-circulation of the above leached slurry inside the above High
Pressure Acid Leach equipment, high-temperature and high-pressure
conditions near a normal operation can be held inside the High
Pressure Acid Leach equipment, in particular, in the means (b),
therefore, operation can be started-up by switching to the ore
slurry soon, if necessary, and high operation efficiency can be
maintained. In addition, different from a conventional shutdown,
switching to industrial water is not necessary, and thus discharged
water is not generated, which contribute to enhancement of
operation efficiency.
[0045] The hydrometallurgical Process for a nickel oxide ore using
the High Pressure Acid Leach relevant to the hydrometallurgical
Process for of the present invention, is one including a
preparation step of ore slurry by making a slurry of a nickel oxide
ore; a leaching step for obtaining leached slurry by transferring
of the ore slurry to the High Pressure Acid Leach equipment
equipped with the following means (a) to (c), for leaching nickel
and cobalt; and a solid-liquid separation step of the leached
slurry, and the total process steps are those shown, for example,
in FIG. 1.
[0046] FIG. 1 is a process chart representing one example of an
embodiment of a hydrometallurgical Process for a nickel oxide ore,
in a normal state, according to a High Pressure Acid Leach.
[0047] In FIG. 1, a nickel oxide ore 6 is firstly subjected to an
ore slurry preparation step 1, to prepare ore slurry 7 including
predetermined ore particle size and slurry concentration, and
subsequently, in a leaching step 2, subjected to High Pressure Acid
Leach using sulfuric acid to form a leached slurry 8. Next, the
leached slurry 8 is subjected to the solid-liquid separation step
3, and after multistage washings, is separated to a leach solution
9 containing nickel and cobalt, and a leaching residue 10. The
leach solution 9 is subjected to a neutralization step 4 to form a
neutralized precipitate slurry 11 containing trivalent iron
hydroxide and a pregnant solution for nickel recovery 12. Lastly,
the pregnant solution for nickel recovery 12 is subjected to a
sulfurization step 5, and is separated to a sulfide 13 containing
nickel and cobalt and a barren solution 14 removed the nickel or
the like. Here, the neutralized precipitate slurry 11 and the
barren solution 14 are circulated to the solid-liquid separation
step 3, if necessary. Still more, prior to the solid-liquid
separation step 3, a step for preliminary neutralization of free
sulfuric acid in the leached slurry 8 (a preliminary neutralization
step), not shown in the drawing, may be provided with.
[0048] Here, in a trouble of the steps other than the above
leaching step 2 (for example, the ore slurry preparation step 1,
the solid-liquid separation step 3, the neutralization step 4, the
sulfurization step 5 or the preliminary neutralization step), the
leached slurry 8 discharged from an apparatus at the exit side of
the High Pressure Acid Leach equipment, which configures the
leaching step 2, is subjected to self-circulation inside the High
Pressure Acid Leach equipment, by shutdown of transfer to the
solid-liquid separation step 3 or the preliminary neutralization
step, and transferring to an apparatus at the entrance side of the
High Pressure Acid Leach equipment, as well as by shutdown of
receiving the above ore slurry 7 and the addition of sulfuric acid,
in the leaching step 2.
[0049] The above nickel oxide ore is not specially limited one but
so-called a lateritic ore such as mainly limonite and saprolite.
Nickel content in the above lateritic ore is usually 0.8 to 2.5% by
weight, and nickel is contained as a hydroxide or a silicic bittern
(magnesium silicate) mineral. In addition, iron content is 10 to
50% by weight, and iron is contained mainly as a trivalent
hydroxide (goethite) form, however, divalent iron is partially
contained in the silicic bittern mineral.
[0050] The leaching step for obtaining the above leached slurry,
that is, a leaching reaction in a normal state of the leaching
step, for example, is performed by the leach reaction represented
by the following formulae (1) to (3), and the high-temperature
hydrolysis represented by the following formulae (4) and (5).
[Leach Reaction]
[0051] Formula (1):
MO+H.sub.2SO.sub.4.fwdarw.MSO.sub.4+H.sub.2O (1)
(wherein M represents Ni, Co, Fe, Zn, Cu, Mg, Cr, Mn or the
like.)
Formula (2):
2Fe(OH).sub.3+3H.sub.2SO.sub.4.fwdarw.Fe.sub.2(SO.sub.4).sub.3+6H.sub.2O
(2)
Formula (3):
FeO+H.sub.2SO.sub.4.fwdarw.FeSO.sub.4+H.sub.2O (3)
[High-Temperature Thermal Hydrolysis]
[0052] Formula (4):
2FeSO.sub.4+H.sub.2SO.sub.4+1/2O.sub.2.fwdarw.Fe.sub.2(SO.sub.4).sub.3+H-
.sub.2O (4)
Formula (5):
Fe.sub.2(SO.sub.4).sub.3+3H.sub.2O.fwdarw.Fe.sub.2O.sub.3+3H.sub.2SO.sub-
.4 (5)
[0053] Temperature in the above leaching step, in a normal state,
is 220 to 280.degree. C., and preferably 240 to 270.degree. C. That
is, iron is fixed as hematite mostly, by performance of the
reaction in this temperature range. In the temperature below
220.degree. C., iron dissolves and remains in the reaction
solution, due to low rate of the high-temperature thermal
hydrolysis, resulting in increase in the solution purification load
for removing the iron, which makes it very difficult to separate
the iron from nickel. On the other hand, the temperature over
280.degree. C. is not suitable, because not only selection of a
material of a reactor to be used for High Pressure Acid Leach is
difficult but also steam cost for raising temperature increases,
although the high-temperature thermal hydrolysis itself is
promoted.
[0054] Slurry concentration in the above leaching step, in a normal
state, is not especially limited, however, it is preferable that
slurry concentration of the leached slurry is adjusted at about 30
to 45% by mass. That is, the leached slurry concentration lower
than 30% by mass requires a large equipment to obtain the same
residence time in leaching, and also the addition amount of an acid
increases to adjust the residual acid concentration. In addition,
the resulting leach solution has lower nickel concentration. On the
other hand, the slurry concentration over 45% by mass raises a
problem of difficult transfer (frequent pipe clogging, high energy
requirement etc.) of high concentration slurry, although it allows
smaller facility scale.
[0055] The addition amount of sulfuric acid in the above leaching
step, in a normal state, is not especially limited, and an excess
amount is used so as to leach iron in a nickel oxide ore, for
example, the amount of 250 to 400 kg per ton of the ore. The
addition amount of sulfuric acid over 400 kg, per one ton of the
ore, is not preferable, due to increased cost of the sulfuric
acid.
[0056] The High Pressure Acid Leach equipment to be used in the
hydrometallurgical Process for of the present invention, is
composed of means of the above (a) to (c), and means of the above
(a) to (c) are not especially limited, however, it is preferable to
use the following apparatus, respectively:
means of (a): a multistage heater for increasing temperature and
pressure of the ore slurry stepwise, means of (b): an autoclave for
leaching the ore slurry at high temperature under high pressure,
and forming the leached slurry with high temperature and high
pressure, and means of (c): a multistage flash tank for decreasing
temperature and pressure of the leached slurry stepwise. Here,
self-circulation of the leached slurry inside the High Pressure
Acid Leach equipment is performed by utilization of a valve on a
pipeline to connect the flash tank and the preliminary
neutralization step or the solid-liquid separation step, and by
installment of a pipeline for self-circulation to connect the valve
and the above heater.
[0057] In the hydrometallurgical Process for of the present
invention, pH of the relevant leached slurry, in self-circulation
of the leached slurry inside the High Pressure Acid Leach
equipment, is not especially limited, however, it is preferable to
be adjusted at 3.0 to 5.0, and more preferably 4.0 to 5.0. That is,
the pH below 3.0 provides low suppression effect of corrosion of
the apparatus. On the other hand, the pH over 5.0 is not preferable
due to increase in use amount of industrial water, that is, also
discharged water amount.
[0058] In the hydrometallurgical Process for of the present
invention, temperature of the means (b), which composes the
relevant High Pressure Acid Leach equipment, in self-circulation of
the leached slurry inside the High Pressure Acid Leach equipment,
is preferably set at 200 to 260.degree. C., and more preferably 220
to 240.degree. C. That is, it is most desirable to maintain
temperature of the above normal state, however, the temperature
below 200.degree. C. decreases shortening effect of heat-up time in
re-startup. On the other hand, the temperature over 260.degree. C.
may require temperature decrease, and thus provides useless
consumption of high-pressure steam. It should be noted that it is
enough to continuously supply and adjust steam to the autoclave in
order to maintain and control temperature.
[0059] The hydrometallurgical Process for of the present invention
can be applied in a trouble of the steps other than the above
leaching step for obtaining the above leached slurry, however, it
is preferable to determine in what a state the High Pressure Acid
Leach equipment shall wait, by judgment of which method is most
suitable in view of operation efficiency, among a countermeasure
method for self-circulation of the leached slurry of the present
invention in the High Pressure Acid Leach equipment, corresponding
to decision of estimated shutdown time in the leaching step
accompanying with the relevant trouble; or a conventional method,
that is a method for cooling by supplying industrial water instead
of the ore slurry, in a connected state of each of the apparatuses;
or a countermeasure method for cooling individually by separation
of each of the apparatuses. In this way, in a practical operation,
in the case of trouble generation in the above other steps,
countermeasure is possible, based on judgment standards, for
example, shown in Table 1, corresponding to estimated shutdown time
of the above leaching step, based on restoration time of each of
the troubles in normal operation.
TABLE-US-00001 TABLE 1 Estimated Countermeasure Basis of judgment
shutdown time method standards* The case Self-circulation Cooling
time: 2 to 3 hours within of the present Heating time: 12 hours
invention 1 to 2 hours Generated waste solution (volume):
.ltoreq.600 m.sup.3 The case over Conventional Cooling time: 6 to 8
hours 12 hours method Heating time: 4 to 6 hours Generated waste
solution (volume): .gtoreq.2000 m.sup.3 *Required values for each
of the countermeasure methods.
[0060] In Table 1, the above estimated shutdown time as a judgment
standard of a countermeasure, is 12 hours. That is, a method for
self-circulation of the leached slurry of the present invention in
the High Pressure Acid Leach equipment is applicable preferably in
the case where the above estimated shutdown time is within 12
hours. Here, reason for setting the above estimated shutdown time,
as a standard, to be within 12 hours is because it requires usually
about 6 to 8 hours to decrease temperature down to 150 to
180.degree. C., and about 4 to 6 hours to increase temperature
again, that is about 12 hours in total, in average, in the case
where the High Pressure Acid Leach equipment is shutdown and
temperature is decreased by separation of each of the apparatuses,
and then temperature is increased again. That is, in the case where
restoration time of troubles is over 12 hours, it is sufficient to
respond to them by a conventional method. It should be noted that,
in the case where restoration time of troubles is over 24 hours, a
countermeasure by further decreasing temperature may be taken, in
consideration of cost of steam to be consumed in warming the
autoclave.
[0061] It should be noted that 12 hours is taken as a guideline, in
the judgment standard in Table 1, however, this is based on a time
required from shutdown to start-up by a conventional countermeasure
method, and thus in the case where this required time varies, the
standard time may be adjusted and varied, as appropriate.
EXAMPLES
[0062] Explanation will be given below in further detail on the
present invention with reference to Example and Comparative Example
of the present invention, however, the present invention should not
be limited to these Examples.
Example 1
[0063] In the hydrometallurgical Process for a nickel oxide ore
using the High Pressure Acid Leach, which process is shown in FIG.
1, countermeasures was prepared to take that, in the case of
generation of a trouble of the steps other than the above leaching
step, the leached slurry discharged from a three-stage flash tank,
which configures the above High Pressure Acid Leach equipment of
the leaching step, is subjected to self-circulation inside the High
Pressure Acid Leach equipment, by transferring to the entrance side
of a three-stage heater, which configures the above High Pressure
Acid Leach equipment, as well as by shutdown of receiving the ore
slurry and the addition of sulfuric acid to the autoclave, in the
above leaching step. It should be noted that pH of the leached
slurry to be self-circulated was controlled at 3.7, and temperature
inside the autoclave at 220.degree. C.
[0064] After one-year of operation performance (from January to
December, 2007), the number of troubles generated during the
relevant period was 6 times, however, a trouble giving estimated
shutdown time of the High Pressure Acid Leach equipment over 12
hours was only once. As a result, shutdown of the High Pressure
Acid Leach equipment was also only once (8 hours). Results are
shown in Table 2.
[0065] It should be noted that troubles caused by corrosion of a
supply pump to the heater, mechanical seal apparatus and the like,
were not observed.
Comparative Example 1
[0066] In the hydrometallurgical Process for a nickel oxide ore
using the High Pressure Acid Leach, which process is shown in FIG.
1, in the case of generation of a trouble of the steps other than
the above leaching step, countermeasure was taken by either of a
method for cooling, by supplying industrial water instead of the
ore slurry, while each of the apparatuses are connected; or a
method for cooling individually, by separation of each of the
apparatuses.
[0067] After one-year of operation performance (from January to
December, 2006), the number of troubles generated during the
relevant period was 7 times, and the High Pressure Acid Leach
equipment was shutdown each time. Results are shown in Table 2.
TABLE-US-00002 TABLE 2 Generated waste Shutdown Shutdown solution
frequency time (volume) Example 1 once/y 8 hours/y 500 m.sup.3/y
Com. 7 times/y 336 hours/y about 15,000 m.sup.3/y Example 1
[0068] From Table 2, it is understood that, in Example 1, because
countermeasures was taken, according to a method of the present
invention, by self-circulation of the leached slurry inside the
High Pressure Acid Leach equipment, in trouble generation, and for
a trouble which estimated shutdown time of the High Pressure Acid
Leach equipment is within 12 hours, shutdown time of the High
Pressure Acid Leach equipment for one year, and discharged water
amount generated are improved to a large extent, as compared with
Comparative Example 1 representing a conventional method. That is,
in Example 1, shutdown time of the High Pressure Acid Leach
equipment for one year becomes equal to 1/40 or lower, as well as
discharged water amount generated becomes about 1/30, showing that
high operation efficiency can be maintained as a whole operation
basis.
[0069] As is clear from the above, the hydrometallurgical Process
for a nickel oxide ore of the present invention, is suitable as a
method for maintaining operation efficiency in trouble generation,
in a hydrometallurgical Process for a nickel oxide ore using a High
Pressure Acid Leach, because it is capable of preventing inevitable
operation shutdown of the above leaching step, and maintaining high
operation efficiency as a whole process basis, in a trouble of the
steps other than the leaching step.
* * * * *